1. Field of the Invention
The invention relates to primer compositions and their preparation, to a process for improving the adhesion of silicone rubber to a substrate, in particular for adhesive bonding of silicone rubber with a substrate, to shaped composite articles and composite materials resulting therefrom, and to their use.
2. Background Art
U.S. Pat. No. 3,769,253 describes primer compositions which contain polydiorganosiloxanes having vinyl groups, organic peroxides, and silanes having acyloxy groups. A major disadvantage of such primers is their non-optimal adhesion to metals. These primer coats have the further disadvantage that, owing to carboxylic acids liberated from the acyloxy groups, both the stability of the silicone elastomer is reduced, and corrosion of the substrate, particularly metal substrates, is promoted.
EP-A 61 871 discloses primer compositions which contain an alkoxy-containing silicon compound, optionally partial hydrolysis condensates thereof, an organic solvent, and a hydroperoxide. If the hydroperoxide is replaced by dialkyl peroxides or diaryl peroxides, poorer adhesion is achieved.
U.S. Pat. No. 6,409,874 describes a process for the preparation of a silicone-metal adhesive bond. Here, the metal substrate or the silicone elastomer substrate is first brought into contact with a mixture of a nonfunctional silane and a functional silane having alkoxy groups, the silanes being partly hydrolyzed, and the two substrates are then combined.